Occasionally, when I am working in Surveyor--- or when in my session and click to transfer to another loco, SUDDENLY, there will be brief but striking flashing of patterns and colors! The flashing will keep on until I scoot away from the loco or scenery to a plain section of the route, like a field or something. When I try to return to the loco, the flashing begins again. So far my session or route hasn't crashed, but this is very frightening. I have a 200 mile route I'm creating and this can be un-nerving. Anyone have any idea what is causing this?